U.S. patent number 11,292,472 [Application Number 17/052,891] was granted by the patent office on 2022-04-05 for method and control device for operating a drivetrain.
This patent grant is currently assigned to ZF Friedrichshafen AG. The grantee listed for this patent is ZF Friedrichshafen AG. Invention is credited to Andreas Heinzler, Mario Steinborn.
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United States Patent |
11,292,472 |
Steinborn , et al. |
April 5, 2022 |
Method and control device for operating a drivetrain
Abstract
A method of operating a motor vehicle drive-train having a drive
aggregate, a group transmission and a drive output. The aggregate
can couple an input shaft of the transmission which includes main,
splitter and range groups. To carry out a shift, a target gear and
target rotational speed of the aggregate are calculated for the
shift to be carried out. After the initiation of the shift a load
reduction is first carried out, then a group of the transmission is
disengaged in order to shift the transmission to neutral, after
which a group of the transmission is synchronized and to shift out
of neutral, the synchronized group is engaged, and then the load is
again built up. Initiation of the shift, after calculating the
target gear and the target rotational speed, occurs at a point in
time when complete performance of a shift is not yet possible.
Inventors: |
Steinborn; Mario
(Friedrichshafen, DE), Heinzler; Andreas (Ravensburg,
DE) |
Applicant: |
Name |
City |
State |
Country |
Type |
ZF Friedrichshafen AG |
Friedrichshafen |
N/A |
DE |
|
|
Assignee: |
ZF Friedrichshafen AG
(Friedrichshafen, DE)
|
Family
ID: |
1000006217451 |
Appl.
No.: |
17/052,891 |
Filed: |
May 6, 2019 |
PCT
Filed: |
May 06, 2019 |
PCT No.: |
PCT/EP2019/061484 |
371(c)(1),(2),(4) Date: |
November 04, 2020 |
PCT
Pub. No.: |
WO2019/219418 |
PCT
Pub. Date: |
November 21, 2019 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20210245761 A1 |
Aug 12, 2021 |
|
Foreign Application Priority Data
|
|
|
|
|
May 18, 2018 [DE] |
|
|
102018207859.9 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B60W
10/04 (20130101); B60W 30/19 (20130101); F16H
61/702 (20130101); B60W 10/02 (20130101); F16H
61/16 (20130101); B60W 10/11 (20130101); B60W
10/111 (20130101); F16H 59/40 (20130101); F16H
61/0403 (20130101); F16H 2059/366 (20130101); B60W
2510/104 (20130101); B60W 2510/0638 (20130101); B60W
2710/021 (20130101); B60W 2710/1005 (20130101) |
Current International
Class: |
B60W
30/19 (20120101); B60W 10/02 (20060101); B60W
10/04 (20060101); B60W 10/11 (20120101); B60W
10/111 (20120101); F16H 59/40 (20060101); F16H
61/04 (20060101); F16H 61/16 (20060101); F16H
61/70 (20060101); F16H 59/36 (20060101) |
Field of
Search: |
;477/110,111,108 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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10 2007 007 257 |
|
Aug 2008 |
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DE |
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10 2007 043 695 |
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Mar 2009 |
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DE |
|
10 2008 040 126 |
|
Jan 2010 |
|
DE |
|
10 2011 080 849 |
|
Feb 2013 |
|
DE |
|
10 2012 203 582 |
|
Sep 2013 |
|
DE |
|
0 578 398 |
|
Jan 1994 |
|
EP |
|
0 584 984 |
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Mar 1994 |
|
EP |
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2 304 275 |
|
Feb 2012 |
|
EP |
|
Other References
German Office Action Corresponding to 10 2018 207 859.9 dated May
9, 2019. cited by applicant .
International Search Report Corresponding to PCT/EP2019/061484
dated Jul. 25, 2019. cited by applicant .
Written Opinion Corresponding to PCT/EP2019/061484 dated Jul. 25,
2019. cited by applicant.
|
Primary Examiner: Pang; Roger L
Attorney, Agent or Firm: Finch & Maloney, PLLC Bujold;
Michael Franklin; Jay
Claims
The invention claimed is:
1. A method for operating a drive-train of a motor vehicle with a
control device, the drive train having a drive aggregate, a group
transmission and a drive output, the drive aggregate being
couplable, via a clutch, to an input shaft of the group
transmission, the group transmission having a main group, and at
least one of a splitter group, that is drive-connected upstream
from the main group, and a range group, that is drive-connected
downstream from the main group, to carry out a shift from a current
gear to a target gear of the group transmission, the target gear
and a target rotational speed of the drive aggregate are calculated
by the control device, after initiation of the shift, a load
reduction is carried out, then a first group of the group
transmission is disengaged in order to shift the group transmission
to neutral, after which a second group of the group transmission is
synchronized and to move out of neutral, the synchronized second
group is engaged, and then the load is built up, the method
comprising: calculating, with the control device, the target gear
and the target rotational speed, subsequent to the calculation,
initiating the shift with the control system at a point in time
when complete performance of a shift is not yet possible, reducing
the load and shifting the group transmission to neutral by
disengaging the first group of the group transmission, subsequently
setting the calculated target rotational speed at the drive
aggregate, with the control device, maintaining the group
transmission in neutral and maintaining the calculated target
rotational speed, which is set at the drive aggregate, until the
second group of the group transmission is synchronized as a result
of a change of a rotational speed at the drive output, and
immediately after synchronization of the second group of the group
transmission, engaging the synchronized second group and shifting
the group transmission out of neutral.
2. The method according to claim 1, further comprising maintaining
the group transmission in neutral and maintaining the calculated
target rotational speed set at the drive aggregate until, within a
defined time interval and as a result of the change of the
rotational speed at the drive output, the second group of the group
transmission is synchronized, whereas, if synchronization of the
second group of the group transmission does not occur within the
defined time interval, at least one of selecting a new target gear,
and adapting the rotational speed of the drive aggregate in order
to achieve synchronization.
3. The method according to claim 1, further comprising, in parallel
with the setting of the target rotational speed at the drive
aggregate while the group transmission is in neutral, at least one
of engaging a third group of the group transmission, and changing a
shift gate in the main transmission to a target position.
4. The method according to claim 1, further comprising, if the
rotational speed at the drive output multiplied by a gear ratio of
the target gear is within a rotational speed window that extends
around the calculated target rotational speed, engaging the second
group of the group transmission that is synchronized in order to
shift out of neutral.
5. The method according to claim 4, further comprising defining the
rotational speed window by a positive offset and a negative offset,
relative to the target rotational speed of the drive aggregate, at
least one of the positive offset and the negative offset is
determined by the control device depending on whether the shift
from the current gear to the target gear is an upshift or a
downshift in traction operation or in an overdrive operation.
6. The method according to claim 1, further comprising when the
group transmission is in neutral and the target rotational speed is
set at the drive aggregate, engaging the clutch far enough to
couple the drive aggregate to the input shaft of the group
transmission such that a rotational speed of the input shaft
corresponds to the rotational speed of the drive aggregate.
7. The method according to claim 1, further comprising when the
synchronized second group of the group transmission is engaged,
disengaging the clutch by which the drive aggregate is coupled to
the input shaft of the group transmission.
8. The method according to claim 1, further comprising defining the
point in time at which complete performance of the shift is not yet
possible as being a point in time at which the target rotational
speed of the drive aggregate has not been reached at the
transmission input.
9. A control device for operating a drive-train of a motor vehicle,
the drive train having a drive aggregate, a group transmission and
a drive output, the drive aggregate is couplable, via a clutch, to
an input shaft of the group transmission, and the group
transmission comprises a main group and at least one of a splitter
group, that is drive-connected upstream from the main group, and a
range group, that is drive-connected downstream from the main
group, to carry out a shift from a current gear to a target gear of
the group transmission, the control device calculating the target
gear and a target rotational speed of the drive aggregate, and
after initiating the shift, reducing the load, and disengaging a
first group of the group transmission to shift the group
transmission to neutral, the control device then synchronizes a
second group of the group transmission and, to shift out of
neutral, engages the synchronized second group and finally builds
up the load, wherein after calculating the target gear and the
target rotational speed, the control device initiates the shift
from the current gear to the target gear at a point in time at
which a complete performance of the shift is not yet possible,
after initiating the shift and after the load reduction and after
shifting the group transmission to neutral, the control device sets
the calculated target rotational speed at the drive aggregate, the
control device keeps the group transmission in neutral and
maintains the calculated target rotational speed at the drive
aggregate until, as a result of a change of a rotational speed at
the drive output, the second group of the group transmission is
synchronized, and immediately after synchronization, the
synchronized second group is engaged and the group transmission is
shifted out of neutral.
10. The control device according to claim 9, wherein the control
device is adapted to initiate the shift from the current gear to
the target gear after calculating the target gear and the target
rotational speed occurs at a point in time when complete
performance of the shift is not yet possible, set the calculated
target rotational speed at the drive aggregate after each of the
shift is initiated, and the load is reduced and the group
transmission is shifted to neutral, maintaining the group
transmission in neutral and maintaining the calculated target
rotational speed, set at the drive aggregate, until, as the result
of the change of the rotational speed at the drive output, the
second group of the group transmission is synchronized, and
immediately after synchronization of the second group, engaging the
synchronized second group and moving the group transmission out of
neutral.
11. A method of operating a motor vehicle drive-train with a
control device, the drive train having a drive aggregate, a group
transmission and a drive output, the drive aggregate being
couplable, via a clutch, to an input shaft of the group
transmission, the group transmission having a main group and at
least one of a splitter group and a range group, the splitter being
drive-connected upstream from the main group and the range group
being drive-connected downstream from the main group, the method
for shifting the group transmission from a current gear to a target
gear comprising: calculating, with the control device, the target
gear and a target rotational speed of the drive aggregate for the
shift to be carried out; subsequently, initiating, with the control
device, the shift at a point in time when complete performance of a
shift is not yet possible, reducing a load and, then shifting the
group transmission to neutral by disengaging a first group of the
group transmission, subsequently, setting, with the control device,
the calculated target rotational speed at the drive aggregate,
maintaining the group transmission in neutral and maintaining the
calculated target rotational speed set at the drive aggregate
until, as the result of a change of a rotational speed at the drive
output, a second group of the group transmission is synchronized,
and immediately after the synchronization of the second group,
engaging the synchronized second group, shifting the group
transmission out of neutral and building up the load.
Description
This application is a National Stage completion of
PCT/EP2019/061484 filed May 6, 2019, which claims priority from
German patent application serial no. 10 2018 207 859.9 filed May
18, 2018.
FIELD OF THE INVENTION
The invention relates to a method and a control device for
operating a drive-train of a motor vehicle.
BACKGROUND OF THE INVENTION
From the prior art drive-trains of motor vehicles are known, which
have a group transmission as their transmission. A group
transmission comprises a main group, a splitter group in drive
connection upstream from the main group and/or a range group in
drive connection downstream from the main group. The main group is
also called the main transmission. Shifting processes in the
splitter group and in the range group can typically be carried out
in a synchronized manner. Typically, shifting processes in the main
group can be carried out without synchronization.
From DE 10 2007 007 257 A1 a method for operating a drive-train
with a group transmission is known. From this prior art, it is
known to use an electric machine during shifting processes in the
group transmission as synchronizing means, a synchronization aid or
a shifting aid.
From EP 2 304 275 B1 a method for carrying out a gearshift in an
automatic transmission of a utility vehicle is known. From this
prior art, it is known that for the shifting process a transmission
control system determines on the one hand a target gear and on the
other hand a target rotational speed associated with the target
gear as a function of certain parameters, such that when a
determined shifting rotational speed is reached the shifting
process is carried out. In this case the shifting rotational speed
is determined in such manner that a complete shift is possible,
i.e. after the shift has been initiated the shift can be
implemented in full.
As a result of the fact that according to the prior art a shift can
only be initiated if the shift can also be completed, before the
shift is initiated, synchronization for a group of the group
transmission that is to be shifted first has to take place.
In methods known from the prior art, synchronization takes place by
way of the drive aggregate, the clutch connected between the drive
aggregate and the transmission input shaft, or a transmission brake
that acts in particular on the transmission input shaft. The result
of this is that the actual target rotational speed of the drive
aggregate often cannot be reached.
There is a need to propose a method for operating a drive-train
with a group transmission, in which method, when carrying out a
shift, a target rotational speed of the drive aggregate can be
produced reliably.
SUMMARY OF THE INVENTION
Starting from there, the purpose of the present invention is to
provide a new type of method for operating a drive-train of a motor
vehicle and a control device for carrying out the method.
This objective is achieved by a method for operating a drive-train
according to the independent claim(s).
According to the invention, the shift is initiated after
calculating the target gear and the target rotational speed at a
point in time when the shift cannot yet be carried out completely.
After the initiation of the shift and after the load reduction and
also after shifting the group transmission to neutral, according to
the invention the calculated target rotational speed is set at the
drive aggregate. According to the invention, the group transmission
remains in neutral and the calculated target rotational speed is
maintained at the drive aggregate until, as a result of a change of
the rotational speed at the drive output, the group of the group
transmission that is to be synchronized has been synchronized, and
immediately after this synchronization in the transmission the
synchronized group is engaged and the group transmission is shifted
out of neutral.
With the present invention it is proposed to initiate the shift
prematurely at a point in time when it is not yet possible to carry
out the shift completely.
After the initiation of the shift, the load reduction and the
change of the group transmission to neutral take place
imperatively, the drive aggregate is adjusted to the target
rotational speed. The group transmission and the drive aggregate
remain in this condition until, as a result of a change of the
drive output rotational speed, the group of the group transmission
that is to be synchronized is actually synchronized, and after that
the synchronized group is engaged, following which the group
transmission is shifted out of neutral. Thus, the rotational speed
of the drive aggregate is held at the desired target rotational
speed during a neutral phase of the group transmission and the
system waits until, by virtue of the driving dynamics, namely a
change of the vehicle's speed, the synchronization of the group of
the group transmission that is to be synchronized has taken place
and the transmission can be shifted out of neutral. In this way the
target rotational speed can be reached safely and reliably.
According to an advantageous further development of the invention,
the group transmission remains in neutral and the calculated target
rotational speed is maintained at the drive aggregate until, within
a defined time interval after a change of the rotational speed at
the drive output, the group of the group transmission to be
synchronized has been synchronized, and if the synchronization in
the transmission does not take place within the defined time
interval, a new target gear is selected and/or the rotational speed
of the drive aggregate is adapted in order to achieve
synchronization. If the synchronization at the drive output is not
successful, then either another target gear can be engaged or the
gearshift initiated can be completed by synchronization of the
transmission input from the drive aggregate side.
Preferably, in parallel with the setting of the target rotational
speed at the drive aggregate while the group transmission is in
neutral, a further group of the group transmission is shifted
and/or in the main transmission a shift gate is changed to a target
position. While the group transmission is in neutral, further
groups of the transmission to be shifted for the gearshift to be
carried out are shifted and/or in the main transmission the shift
gate is changed to the target position. Accordingly, while in
neutral, the group transmission is prepared to the extent that by
closing the group of the group transmission that is to be
synchronized, the transmission can be moved out of neutral
rapidly.
According to an advantageous further development, the group of the
group transmission synchronized by the
transmission-drive-output-side synchronization is engaged in order
to shift out of neutral when the rotational speed at the drive
output multiplied by the gear ratio of the target gear reaches a
rotational speed window that extends around the calculated target
rotational speed. Preferably, the rotational speed window is
defined by a positive offset and a negative offset relative to the
calculated target rotational speed, such that the positive offset
and/or the negative offset is/are determined depending on whether
in the group transmission an upshift or a downshift is to be
carried out in traction operation or in overdrive operation. By
closing the synchronized group of the group transmission when the
defined rotational speed window for the target rotational speed of
the transmission input shaft has been reached, which corresponds to
the rotational speed at the drive output multiplied by the gear
ratio of the target gear, the transmission can be moved out of
neutral reliably. By selecting the corresponding offsets, the shift
can be optimally coordinated, and this indeed while avoiding or
eliminating tooth-on-tooth situations at a shifting element of a
group of the transmission that is to be closed, in particular at a
shifting element of the main group.
In an advantageous further development, while the group
transmission is in neutral and the calculated target rotational
speed has been set at the drive aggregate, the clutch is closed far
enough for a rotational speed of the input shaft to match the
rotational speed of the drive aggregate. Then, when the
synchronized group of the group transmission is shifted the clutch,
via which the drive aggregate is coupled to the input shaft of the
group transmission, is preferably opened. If the clutch is opened
during the shifting of the group of the group transmission being
synchronized, the comfort while carrying out the gearshift can be
increased.
The control device according to the invention for operating a
drive-train of a motor vehicle is defined in the independent
claim(s).
BRIEF DESCRIPTION OF THE DRAWINGS
Preferred further developments emerge from the subordinate claims
and from the description that follows. Example embodiments of the
invention, to which it is not limited, are explained in greater
detail with reference to the drawings, which show:
FIG. 1: An example of a layout of a drive-train of a motor vehicle
with a group transmission, and
FIG. 2: A time diagram to clarify the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention relates to a method for operating a
drive-train of a motor vehicle and to a control device for carrying
out the method.
FIG. 1 shows the layout of a drive-train of a motor vehicle with a
drive aggregate 1, a group transmission 2 and a drive output 3. In
addition FIG. 1 shows a control device 4 for operating the group
transmission 2. The drive aggregate 1 can be coupled by a separator
clutch 5, also called a starting clutch, to an input shaft 6 of the
group transmission 2. The drive output 3 is coupled to an output
shaft 8 of the group transmission 2.
In the example embodiment shown, the group transmission 2 comprises
a main group 9, a splitter group 10 drive-connected upstream from
the main group 9 and a range group 11 drive-connected downstream
from the main group 9. The group transmission 2 can also comprise
only the splitter group 10 or the range group 11 apart from the
main group 9.
In the example embodiment shown, the main group 9 of the group
transmission 2 is a direct-gear transmission of countershaft
design, with two countershafts 21, 22. In the example embodiment
shown, the main group 9 is made with three gear steps G1, G2 and G3
for forward driving and with one gear step R for driving in
reverse. Loose wheels of the gear steps G1, G2 and R are in each
case mounted to rotate on a main shaft 7 and can be engaged by
associated shifting elements 15, 16, 18 and 19 in the form of claw
clutches.
The associated fixed wheels are arranged rotationally fixed on the
countershafts 21, 22. The two shifting elements 15, 16 and the two
shifting elements 18, 19 form in each case a shifting packet 17 and
20 respectively. The main group 9 can be shifted without
synchronization.
In the example embodiment shown, the splitter group 10 of the group
transmission 2 is made with two steps and is also of countershaft
design, wherein the two gear ratio steps K1 and K2 of the splitter
group 10 form two switchable input constants of the main group 9.
The two gear ratio steps K1, K2 have a small ratio difference.
The loose wheel of the first gear ratio step K1 is mounted and can
rotate on the input shaft 6. The loose wheel of the second gear
ratio step K2 is mounted and can rotate on the main shaft 7. The
fixed wheels of the two gear ratio steps K1, K2 of the splitter
group 10 are respectively arranged in a rotationally fixed manner
on the countershafts 21, 22 of the main group 9, which are extended
on the input side. Shifting elements 12, 13 of synchronized design,
i.e. so-termed synchronous shifting elements of the splitter group
10, are combined in a common shifting packet 14.
The optional range group 11 of the group transmission 2 arranged
downstream from the main group 9 is also of two-step design, but in
the form of a planetary gearset 24. The sun gear 25 is connected
rotationally fixed to the main shaft 7 of the main group 9 which is
extended on the output side. The planetary carrier 27 is coupled
rotationally fixed with the output shaft 8 of the group
transmission 2. The ring gear 26 is connected to a shifting packet
23 which has two synchronized shifting clutches, by means of which
the range group 11 can be selectively shifted in a synchronized
manner, either by connecting the ring gear 26 to a fixed part of
the housing into a `slow` driving range L or, by connecting the
ring gear 26 to the planetary carrier 27 into a `fast` driving
range S. The range group 11 can be shifted in a synchronized
manner.
The present invention now relates to a method for operating a
drive-train with a group transmission 2, namely for carrying out a
shift from a current gear to a target gear of the group
transmission 2.
In order to carry out a shift in the group transmission 2, namely a
shift from a current gear to a target gear of the group
transmission 2, for the shift to be carried out the control system
first calculates the target gear and a target rotational speed of
the drive aggregate that is appropriate for the target gear.
Typically, the calculation of the target gear takes place as a
function of the driver's wish and as a function of the vehicle
dynamics, wherein details for the calculation of a target gear of a
shift to be carried out will be familiar to one who has knowledge
of the field, to whom this is addressed. Likewise, the calculation
of a target rotational speed of the drive aggregate 1 for a shift
to be carried out will be familiar to the knowledgeable person.
According to the invention, it is proposed that after calculating
the target gear and the target rotational speed, the shift to be
carried out is initiated at a point in time at which a complete
shift is actually not yet possible, i.e. at which the target
rotational speed of the drive aggregate has not been reached at the
transmission input. Compared with methods known from the prior art,
the control system accordingly carries out a premature initiation
of the shift to be performed. After the shift has been initiated, a
load decrease first takes place by way of the drive aggregate 1
and/or the clutch 5, and then the group transmission 2 is shifted
to neutral in that a group of the group transmission 2 is
disengaged.
The disengagement of a group of the group transmission 2 can also
be called the disconnection or opening of the group of the group
transmission 2.
After the load has been reduced and the group transmission 2 has
been shifted to neutral, this condition of the group transmission 2
is maintained, i.e. the group transmission remains in neutral and
the calculated target rotational speed set at the drive aggregate 1
is maintained until, as the result of a rotational speed change at
the drive output 3, the group of the group transmission to be
synchronized has been synchronized, and immediately after this
synchronization, this time on the transmission output side, the
synchronized group is engaged and the group transmission is shifted
out of neutral.
The engagement of the synchronized group of the group transmission
2 can also be called the connection or closing of the group of the
group transmission 2.
For the purposes of the invention it is thus necessary to set and
maintain, at the drive aggregate 1, a desired target rotational
speed while the group transmission 2 is in neutral, and this indeed
until the dynamics of the vehicle make it possible to close the
group of the group transmission 2 that is to be synchronized. The
synchronization of the group of the group transmission 2 to be
synchronized takes place by passively changing the speed of the
vehicle, for example when driving uphill or downhill, i.e. by
changing the rotational speed at the transmission output 8 and not,
as is usual in common practice, by actuating the clutch 5 or by
actuating a transmission brake (not shown).
After the load has been reduced, the group transmission has been
shifted into neutral and the target rotational speed has been set
at the drive aggregate 1, the clutch 5 is actuated in such manner
that it transmits a torque such that the rotational speed of the
input shaft 6 of the group transmission 2 corresponds to the target
rotational speed of the drive aggregate 2. When the gear of the
synchronized group of the group transmission 2 has been engaged or
connected, the clutch 5 can either remain in its closed position
or, to increase comfort, it can preferably be opened.
Further details of the invention are described below with reference
to FIG. 2, which shows the variations with time of a number of time
curves 28, 29, 30 and 32. In FIG. 2 the curve 28 shows the
variation of the rotational speed of the drive aggregate 1. The
curve 29 depicts the variation of the rotational speed at the input
shaft 6 of the group transmission 2. The curve 30 shows the
variation of the rotational speed at the drive output 3 or output
shaft 8 of the group transmission 2. The rotational speed curve 32
depicts, over time, the variation of the target rotational speed
for the input shaft 6 of the group transmission 2, which
corresponds to the product of the rotational speed at the drive
output 3 and the gear ratio of the target gear of the gearshift to
be carried out. In addition a rotational speed window 31 is shown,
which is defined by an upper limit value 31a and a lower limit
value 31b.
At time t1 a shift request is made and accordingly, at time t1 the
target gear and the target rotational speed of the drive aggregate
1 appropriate for the target gear are calculated. Furthermore, in
FIG. 2 directly at time t1 the shift to be carried out is initiated
and for this, as already mentioned, the load is reduced and the
group transmission 2 is shifted to neutral. At time t1 the target
rotational speed for the transmission input shaft 6 jumps upward
since at time t1 the gear ratio changes to that of the new target
gear of the shift to be carried out.
FIG. 2 shows the curve shapes for a downshift to be carried out
while driving uphill.
At time t1 or immediately after time t1, the group transmission 2
is in neutral. Furthermore at time t1, as the shape of curve 28
shows, the rotational speed of the drive aggregate 1 corresponds to
the target rotational speed. Beginning at time t1, the transmission
2 is then held in that condition so the group transmission 2
remains in neutral. The drive aggregate 1 is held at the target
rotational speed 28, and the clutch 5 is closed far enough for the
rotational speed of the transmission input shaft 6 of the group
transmission 2 to correspond to the target rotational speed of the
drive aggregate 1.
In neutral, the rotational speed of the drive output 3 and the
rotational speed of the output shaft 8 of the group transmission 2
now changes in accordance with the curve 30 due to the uphill
driving of the motor vehicle. Furthermore, this reduces the target
rotational speed for the input shaft 6 of the group transmission 2,
which corresponds to the product of the rotational speed of the
drive output 3 and the gear ratio of the target gear. When this
target rotational speed for the input shaft 6 of the group
transmission 2 reaches a rotational speed window 31 that extends
around the target rotational speed 28 of the drive aggregate 1, and
indeed in FIG. 2 intersects the upper limit value 31a, which in
FIG. 2 takes place at time t2, the now synchronized group of the
group transmission 2 leaves neutral by being shifted or engaged or
closed.
Before the time-point t2, and indeed between times t1 and t2,
between which the group transmission 2 is in neutral and between
which the rotational speed of the drive aggregate 1 is set at the
target rotational speed of the gearshift to be carried out, further
groups in the group transmission 2 can be prepared for the
gearshift, so it is possible to shift the splitter group or the
range group if necessary and/or in the main transmission to change
a shift gate to a target position for the shift change to be
carried out.
When at time t2 the transmission is still in neutral and the target
rotational speed for the input shaft 6 of the group transmission 2
reaches the rotational speed window 31, neutral can be left
immediately by shifting or closing the now synchronized group of
the group transmission 2, so that the target gear can be engaged
within the shortest time when the target rotational speed of the
drive aggregate 1 is reached.
At the latest at time t3, at which the target rotational speed of
the input shaft 6 of the group transmission 2 would leave the
rotational speed window 31 again, the shift in the group
transmission 2 is completed.
Leaving neutral takes place when, as already described with
reference to FIG. 2, the target rotational speed of the input shaft
6 of the group transmission 2, which corresponds to the product of
the drive output rotational speed and the gear ratio of the target
gear, reaches the rotational speed window 31. The rotational speed
window 31 is positioned around the target rotational speed 28 of
the drive aggregate 1, and this indeed with a positive offset to
the upper limit value 31a and a negative offset to the lower limit
value 31b. The positive offset and the negative offset can be
quantitatively the same, but they can also be different from one
another. In particular it is provided that the rotational speed
window 31 is defined by a positive offset and a negative offset
such that both the positive offset and the negative offset are
determined by whether in the group transmission an upshift or a
downshift in traction operation or in overdrive is being carried
out. The offsets for upshifts, downshifts, traction operation and
overdrive operation are stored in the control unit 4.
By selecting the offset it is also possible to avoid or eliminate a
tooth-on-tooth position at an interlocking shifting element that
has to be closed. By virtue of the vehicle's dynamics and the
maintenance of the rotational speed of the drive aggregate 1 at the
target rotational speed, intersecting rotational speed rotational
speed behaviors occur at a shifting element that is to be closed,
whereby tooth-on-tooth positions can either be avoided or
eliminated on the drive output side.
As already mentioned, FIG. 2 shows the curves obtained when a
downshift is carried out while driving uphill. The invention is not
limited to this application. Rather, the invention can also be used
when an upshift has to be carried out while driving downhill. In
that case the curve shape runs not downward but upward, as also
does the shape 30 of the drive output rotational speed.
The invention also relates to a control device 4 for carrying out
the method. The control device implements the method by control
means. The control device 4 initiates a shift prematurely after the
target gear and the target rotational speed have been calculated,
at a point in time when complete performance of the shift is
actually not yet possible, i.e. when the target rotational speed of
the drive aggregate 1 has not yet been reached at the transmission
input. After the initiation of the shift, the control device
reduces the load and changes the group transmission to neutral, and
in addition sets the calculated target rotational speed at the
drive aggregate 1. The control device 4 keeps the group
transmission in neutral and maintains the drive aggregate 1 at the
calculated target rotational speed until, owing to a change of the
rotational speed at the drive output 3, the group of the group
transmission 2 to be synchronized has been synchronized, and
immediately after this transmission-output-side synchronization the
synchronized group of the group transmission 2 is engaged or closed
so that then the group transmission can move out of neutral.
INDEXES
1 Drive aggregate 2 Group transmission 3 Drive output 4 Control
device 5 Separator clutch 6 Input shaft 7 Main shaft 8 Output shaft
9 Main group 10 Splitter group 11 Range group 12 Synchronous
shifting element 13 Synchronous shifting element 14 Shifting packet
15 Shifting element 16 Shifting element 17 Shifting packet 18
Shifting element 19 Shifting element 20 Shifting packet 21
Countershaft 22 Countershaft 23 Shifting packet 24 Planetary
gearset 25 Sun gear 26 Ring gear 27 Planetary carrier 28 Curve
shape/Rotational speed of the drive aggregate 29 Curve
shape/Rotational speed of the transmission input shaft 30 Curve
shape/Rotational speed of the drive output 31 Rotational speed
window 31a Upper limit value of the rotational speed window 31b
Lower limit value of the rotational speed window 32 Curve
shape/Target rotational speed of the transmission input shaft
* * * * *